1. Field of the Invention
The present invention relates to a method for correcting a quantity of light emitted from light emitting elements in a case in which quantities of light beams emitted from light emitting portions of three colors are controlled based on digital image data and an image is scanned and recorded on a photosensitive material, a plurality of light emitting elements being provided for at least one of the light emitting portions of three colors.
2. Description of the Related Art
A number of image recording apparatuses each having a digital exposure system mounted thereon has been nowadays developed. Generally, in the digital exposure system, an image is recorded on a recording medium in such a manner that a light beam outputted from a semiconductor laser is modulated with image data and the light beam is deflected by high-speed rotation of a polygon mirror (main scanning), and further the light beam reflected by the polygon mirror is subjected to sub-scanning with a galvano mirror or the like, or the above main scanning is effected repeatedly while moving the recording medium (or moving the recording medium stepwise). Here, as the recording medium, a photosensitive drum electrified by corona discharge, a plane photosensitive material, or the like may be used. Further, in place of the semiconductor laser, other light emitter such as an LED may be used as a light source.
On the other hand, there exists an image recording apparatus in which, after an image has been recorded on a photosensitive material, the image is transferred to an image receiving material by heat development-transfer processing with the photosensitive material and the image receiving material overlapping each other. This apparatus includes a so-called analog exposure system (in this case, slit exposure is generally used in which light is irradiated on an original material and the light reflected therefrom is sequentially guided to the photosensitive material) and a digital exposure system, which are used to record the image on the photosensitive material.
Further, the above image recording apparatus allows the image to be recorded on an image receiving material having substantially the same quality as that of general paper and can select the analog exposure system or the digital exposure system as described above. For this reason, this image recording apparatus is suitably applied to various fields.
Moreover, there is proposed that a plurality of light emitting diodes is provided as light sources for each color and a plurality of lines is recorded simultaneously at one main scanning operation.
On the other hand, in the case of digital exposure, the quantity of light which reaches the photosensitive material is controlled based on image data at the point in time when light is irradiated from a light source or on an optical path. However, due to deterioration of the light source itself, variation of a power source for the light source, dirt of an optical system, or the like, an error may occur between the quantity of light which actually reaches the photosensitive material and the quantity of light obtained by calculation from the image data.
In order to solve the above-described drawback, correction of the quantity of light is effected as occasion demands in such a manner that a photoelectric converting element such as a photo-sensor is provided in a region with no image recorded thereon in the vicinity of the photosensitive material, a quantity of light on the surface of the photosensitive material is detected periodically (for each main scanning, for each image, or for each group of a plurality of images), and the detected value and the calculated value are compared with each other.
Here, a conventional method for correcting quantity of light is provided on condition that images are recorded for each line at the time of main scanning by a conventional image recording apparatus, and therefore, it suffices that only balance between colors be adjusted. Further, since a plurality of light sources is used to increase the quantity of light for one line, the balance of the quantity of light between the light emitting elements of the same color was out of the question.